Control apparatus for vehicle

ABSTRACT

Lane keeping control is ended in accurate timing which does not give an uncomfortable feeling to a driver. In a vehicle  10  which is provided with a steering mechanism  200,  an EPS actuator  300,  and a VGRS actuator  500  and which can change a rudder angle regardless of a driver&#39;s steering input due to the cooperative control of the aforementioned mechanism and actuators, an ECU  100  performs LKA end control. In the control, in cases where a winker lever  16  is operated in a period of performing LKA control for making the vehicle  10  follow a target driving route, if the indicated direction of the winker lever  16  is different from a generation direction of generating an assist steering torque TA of the EPS actuator  300  in the LKA control, the LKA control is promptly ended. In cases where the indicated direction is equal to the generation direction, if a steering angle MAdrv corresponding to the driver&#39;s steering input exceeds a steering angle MAlka generated by the LKA control, the LKA control is ended.

TECHNICAL FIELD

The present invention relates to a control apparatus for a vehicle forcontrolling a vehicle capable of performing lane keeping control, suchas Lane Keeping Assist (LKA), by using a steering mechanism, such as anactive steering mechanism.

BACKGROUND ART

As this type of apparatus, there has been suggested an apparatus forissuing a warning if a vehicle departs from a lane (e.g. refer to apatent document 1). According to a lane departure warning apparatus fora vehicle disclosed in the patent document 1, a passenger and/or adriver is not troubled by that the warning is not issued if thedeparture direction of the vehicle is equal to the indicated directionof a winker or direction indicator in cases where it is judged that thevehicle departs from a driving lane while the winker is in operation.

Moreover, there has been also suggested an apparatus for evaluating thepossibility of steering by the driver and for varying easiness instopping the steering control in order to solve such a problem that thestop timing of steering control can give an uncomfortable feeling to adriver if the steering control is stopped in accordance with theblinking operation of the winker (e.g. refer to a patent document 2).

Moreover, there has been also suggested an apparatus for judging thatthe driver consciously changes the lane and for setting a departurejudgment flag to be OFF if a direction indicated by a direction switchsignal is equal to a direction indicated by the departure direction(e.g. refer to a patent document 3).

Moreover, there has been also suggested an apparatus for changing asteering assist torque if a winker operating direction is equal to asteering direction (e.g. refer to a patent document 4).

PRIOR ART DOCUMENT Patent Document

Patent document 1: Japanese Patent Application Laid Open No. 2006-069323

Patent document 2: Japanese Patent Application Laid Open No. 2007-313978

Patent document 3: Japanese Patent Application Laid Open No. 2007-296920

Patent document 4: Japanese Patent Application Laid Open No. 2002-274402

DISCLOSURE OF INVENTION Subject to be Solved by the Invention

In the vehicle capable of performing this type of lane keeping control,in cases where a winker operation is performed during the implementationof the lane keeping control, if the winker operation is considered to bea type of driver input, there arises a need to end the lane keepingcontrol. However, in the lane keeping control, a steering force forpromoting the steering of steered wheels is applied to the steeredwheels to a greater or lesser degree. Thus, if the lane keeping controlis ended due to this type of winker operation, the deflection of thevehicle associated with the end of the lane keeping control will bedifferent from a direction intended by the driver, and that sometimesgives an uncomfortable feeling to the driver. In the technical ideasdisclosed in the patent documents described above, the uncomfortablefeeling given to the driver by this type of vehicle deflection is notconsidered.

In other words, the conventional technologies exemplified in the patentdocuments have such a technical problem that the vehicle may deflect ina direction which is not intended by the driver when the lane keepingcontrol is ended by the operations of the direction indicator. In viewof the aforementioned problem, it is therefore an object of the presentinvention to provide a control apparatus for a vehicle capable of endingthe lane keeping control without giving the uncomfortable feeling to thedriver.

Means for Solving the Subject

The above object of the present invention can be achieved by a controlapparatus for a vehicle provided with a steering mechanism capable ofchanging a rudder angle of steered wheels regardless of a driver'ssteering input, the control apparatus provided with: a performing devicefor performing predetermined lane keeping control for controlling thesteering mechanism such that the vehicle does not depart from a targetdriving route, in response to a lane keeping request; and an endingdevice for ending the lane keeping control on the basis of an operatingstate of a direction indicator and a control state of the steeringmechanism in a period of performing the lane keeping control.

The vehicle of the present invention is a vehicle provided with thesteering mechanism capable of changing the rudder angle (i.e. actualrudder angle) of the steered wheels regardless of the driver's steeringinput (preferably meaning the input of a steering torque which can begiven via an operating device for promoting the steering operation ofthe driver, such as a steering wheel, the performance of an operationaccompanied by a change in a steering angle (i.e. the operating angle orrotation angle of the operating device), or the like).

The control apparatus for the vehicle of the present invention is acontrol apparatus of the vehicle and can adopt forms of various computersystems such as various processing units like a single or a plurality ofElectronic Control Units (ECUs) or the like, various controllers ormicrocomputer apparatuses, which can include one or a plurality ofCentral Processing Units (CPUs), Micro Processing Units (MPUs), variousprocessors or various controllers, or various memory devices such as aRead Only Memory (ROM), a Random Access Memory (RAM), a buffer memory ora flush memory, as occasion demands.

There can be various practical aspects of the steering mechanism of thepresent invention. For example, the steering mechanism of the presentinvention may be: (1) an electrical rudder angle varying mechanismreferred to as a Steer By Wire (hereinafter abbreviated as a “SBW” asoccasion demands) or the like, which can directly or indirectly apply tothe steered wheels a steering force for promoting the change in therudder angle independently of the steering angle; (2) variouselectronically-controlled power steering apparatuses such as a so-calledElectronic Controlled Power Steering (EPS) which can assist therotational motions of a steering shaft and a pinion gear or the linearmotion of a rack bar engaging with the pinion gear, due to the supply ofthe steering torque from a rotating electrical machine such as a motor;(3) a transmission ratio varying apparatus such as a Variable Gear RatioSteering (VGRS) which can vary a change ratio of the rudder angle withrespect to the steering angle, i.e. a rudder angle transmission ratio(e.g. a value obtained by dividing the steering angle by the actualrudder angle); or another mechanism.

According to the control apparatus for the vehicle of the presentinvention, in its operation, the lane keeping control is performed bythe performing device in response to the lane keeping request, and alane keeping function such as, for example, LKA, is added to thevehicle. The lane keeping control means as its concept that an object(including, for example, a white line (which does not simply mean thatthe color is white), a lane marker, or the like) is recognized by aproper detecting device (e.g. an in-vehicle camera or the like) and therudder angle is controlled automatically (incidentally, in this case,the wording “automatically” means that it is independent of the driver'ssteering input) such that the driving lane of the vehicle is maintainedto a lane defined by the object (in other words, such that the vehicledoes not depart from the object).

On the other hand, from the viewpoint that the driver's will isprioritized, it is desirable that the lane keeping control is endedwithout delay if the driver's steering will is shown in a proper form(e.g. by the steering operation or the operation of the directionindicator, or the like). In other words, in performing the lane keepingcontrol, basically, there is no driver's steering input.

Here, when this type of lane keeping control which can be performedindependently of the driver's steering input is ended in accordance withthe operation of the direction indicator, the vehicle may deflect insome cases, which is not intended by the driver. Specifically, in thesituation that the steering force is applied to the steered wheels (e.g.the steering torque is applied to the steering shaft) by the steeringmechanism just before the end of the lane keeping control, if theapplication of the steering force is stopped (incidentally, beinginstantly stopped and being gradually reduced are basically the same),the steered wheels are steered (the rudder angle is returned) in adirection opposite to a direction of applying the steering force.However, the operation of the direction indicator is not necessarilyaccompanied by a physical or electrical steering input although itindicates the driver's steering will. Thus, when the operation of thedirection indicator is merely performed, the vehicle deflects due to thesteering phenomenon of the steered wheels associated with the end of thelane keeping control. The deflection of the vehicle can occur in thesame manner, regardless of whether the steering mechanism is controlledto change the steering angle or not to change the steering angle(including a case where the change is sufficiently small) when the lanekeeping control is performed. Moreover, the deflection of the vehicle isnot caused by the driver's will. Thus, the driver will highly likelyfeel uncomfortable about the deflection of the vehicle. In particular,if the steering mechanism is controlled not to change the rudder anglewhen the lane keeping control is performed, the driver will likely feelremarkably uncomfortable.

Thus, in the control apparatus for the vehicle of the present invention,the ending device ends the lane keeping control on the basis of theoperating state of the direction indicator and the control state of thesteering mechanism in the period of performing the lane keeping control.

How the deflection of the vehicle, which can occur in ending the lanekeeping control, is perceived by the driver depends significantly on theoperating state of the direction indicator, such as whether or not thedirection indicator is operated or in which direction the indicateddirection of the direction indicator is, and the control state of thesteering mechanism including whether or not the steering force orsteering torque is applied in performing the lane keeping control or itsapplication direction, or whether or not there is the driver's steeringinput.

Therefore, as described above, it is possible to reduce theuncomfortable feeling given to the driver at least to some extent, byending the lane keeping control while determining or selecting thevarious end aspects of the lane keeping control as occasion demands,such as whether to end the lane keeping control promptly, whether tocontinue the lane keeping control over a certain or uncertain period, inwhich timing a process associated with the end is started, in whichtiming the process associated with the end is completed, whether it isto be ended with a stepwise or continuous steering force or a gradualreduction in the steering torque, and the like, on the basis of theoperating state of the direction indicator and the control state of thesteering mechanism.

In one aspect of the control apparatus for the vehicle of the presentinvention, the control state is a generation direction of generating asteering torque in a course of performing the lane keeping control, theoperating state is an indicated direction of the direction indicator,and the ending device changes end timing of the lane keeping control inaccordance with whether or not the generation direction is equal to theindicated direction.

If the generation direction of the steering torque in the course ofperforming the lane keeping control is equal to the indicated directionof the direction indicator (i.e. the direction intended by the driver),the deflection direction of the vehicle in ending the lane keepingcontrol is opposite to the indicated direction. On the other hand, ifthe generation direction of the steering torque is different from theindicated direction of the direction indicator, the deflection directionof the vehicle in ending the lane keeping control is equal to theindicated direction. The deflection of the vehicle which is not intendedby the driver corresponds simply to the former case. Thus, according tothis aspect, the generation of the uncomfortable feeling in ending thelane keeping control is suppressed, effectively and efficiently.

Incidentally, in this aspect, the ending device may end the lane keepingcontrol belatedly in comparison with a case where the generationdirection is different from the indicated direction, if the generationdirection is equal to the indicated direction.

As described above, by delaying the end of the lane keeping control, thedeflection of the vehicle associated with the end of the lane keepingcontrol no longer occurs at least as a series of phenomena linked to theoperation of the direction indicator. Thus, it is effective insuppressing the generation of the uncomfortable feeling.

Moreover, in this aspect, the ending device may end the lane keepingcontrol after the steering input is performed, if the generationdirection is equal to the indicated direction.

If the lane keeping control is ended after the steering input by thedriver (which may cause the change in the steering angle or which may bethe input of the steering torque) is performed (i.e. in other words, ifthe lane keeping control is maintained until the steering input takesplace), at least the driver performs the steering operationcorresponding to the driver's steering will at a time point of startingthe process associated with the end of the lane keeping control. Thus,even if the vehicle deflects, the magnitude of the deflection is small.Moreover, depending on the magnitude of the steering input, it ispossible to suppress the deflection of the vehicle. Therefore, it iseffective in suppressing the uncomfortable feeling given to the driver.

Moreover, in this aspect, the ending device may end the lane keepingcontrol at a time point of performing an operation of the directionindicator, if the generation direction is different from the indicateddirection.

If the generation direction of the steering torque is different from theindicated direction of the direction indicator, as described above, thechange in the rudder angle which occurs in ending the lane keepingcontrol is equal to the indicated direction. Thus, the deflection of thevehicle matches the driver's will regardless of whether or not there isthe steering input. Therefore, even if the lane keeping control is endedat the time point of operating the direction indicator, there will be noproblem in practice. Moreover, since the driver's steering will isreflected as quickly as possible, it is preferable.

In another aspect of the control apparatus for the vehicle or thepresent invention, the ending device ends the lane keeping control if asteering torque is inputted and the inputted steering torque exceeds athreshold value determined in accordance with the inputted steeringtorque in a case where the direction indicator is operated.

According to this aspect, firstly, the steering torque is inputted bythe driver at the time point of starting the process associated with theend of the lane keeping control. Thus, the vehicle does not deflect asthe lane keeping control is ended. Moreover, depending on the seeing ofthe threshold value, it is possible to certainly prevent theuncomfortable feeling from being given to the driver.

Moreover, secondly, the steering torque as the steering input isoverridden by the steering torque supplied to the steering shaft by thesteering mechanism in the course of performing the lane keeping control.Thus, if the direction of the steering torque in the course ofperforming the lane keeping control is equal to the direction of thesteering torque as the steering input (i.e. which is a steeringdirection and which is the indicated direction of the directionindicator as long as the driver does not make a mistake), the steeringtorque as the steering input is relatively small. On the other hand, ifthe direction of the steering torque in the course of performing thelane keeping control is different from the direction of the steeringtorque as the steering input, the steering torque as the steering inputis relatively large. By using this phenomenon, it is easy and possibleto judge the indicated direction of the direction indicator by using thesteering torque as the steering input.

Therefore, by taking such measures that the threshold value is set to belarge in an area in which the steering torque as the steering input isrelatively small and that the threshold value is set to be small in anarea in which the steering torque as the steering input is relativelylarge or similar measures, it is possible to suppress the uncomfortablefeeling given to the driver.

The operation and other advantages of the present invention will becomemore apparent from the embodiments explained below.

Mode for Carrying Out the Invention

Hereinafter, various embodiments of the control apparatus for thevehicle in the present invention will be explained with reference to thedrawings as occasion demands.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram conceptually showing thestructure of a vehicle in a first embodiment of the present invention.

FIG. 2 is a flowchart showing LKA end control performed in the vehiclein FIG. 1.

FIG. 3 is a flowchart showing a LKA end judging process performed in theLKA end control in FIG. 2.

FIG. 4 is a flowchart showing a LKA end judging process in a secondembodiment of the present invention.

FIG. 5 is a schematic characteristic diagram showing a relation betweena steering torque MT and a steering torque threshold value MTth referredto in the LKA end judging process in FIG. 4.

FIRST EMBODIMENT Configuration of Embodiment

Firstly, with reference to FIG. 1, the structure of a vehicle 10 in afirst embodiment of the present invention will be explained. FIG. 1 is aschematic configuration diagram conceptually showing the structure ofthe vehicle 10.

In FIG. 1, the vehicle 10 is provided with a pair of front wheels FL andFR on either sides as steered wheels, and it is configured to move in adesired direction by steering the front wheels. The vehicle 10 isprovided with an ECU 100, a steering mechanism 200, an EPS actuator 300,an EPS driving apparatus 400, a VGRS actuator 500, and a VGRS drivingapparatus 600.

The ECU 100 is provided with a CPU, a ROM, and a RAM, each of which isnot illustrated, and it is an electronic control unit capable ofcontrolling all the operations of the vehicle 10. The ECU 100 is oneexample of the “control apparatus for the vehicle” of the presentinvention. The ECU 100 is configured to perform LKA end controldescribed later, in accordance with a control program stored in the ROM.

Incidentally, the ECU 100 is a unified or one-body electronic controlunit, configured to function as one example of each of the “performingdevice” and the “ending device” of the present invention. The operationsof each of the devices are all performed by the ECU 100. However, thephysical, mechanical and electrical configurations of each of thedevices of the present invention are not limited to this, and each ofthe devices may be configured as various computer systems, such as aplurality of ECUs, various processing units, various controllers, ormicro computer apparatuses.

The steering mechanism 200 is a transmission mechanism for transmittinga steering operation performed by a driver to each of the steeredwheels. The steering mechanism 200 is provided with a steering wheel210, a steering column 220, an upper steering shaft 230, a lowersteering shaft 240, a pinion gear 250, and a rack bar 260.

The steering wheel 210 is an operating device for promoting the steeringoperation performed by the driver.

The steering column 220 is a case unit for accommodating the rotatingshaft of the steering wheel 210.

The upper steering shaft 230 is a steering input shaft coupled with thesteering wheel 210 via the steering column 220, and it is configured torotate substantially integrally with the steering wheel 210.

The lower steering shaft 240 is a steering output shaft coupled with theupper steering shaft 230 via the VGRS actuator 500 described later atone end. The other end of the lower steering shaft 240 is coupled withthe pinion gear 250 accommodated in a steering gear box (whose referencenumeral is omitted). Incidentally, the lower steering shaft 240 and thepinion gear 250 may be coupled directly or indirectly via a propermediate mechanism.

The pinion gear 250 is a gear part which is configured to rotatesubstantially integrally with the lower steering shaft 240 and in whichgear teeth are formed on its outer circumferential surface. The gearteeth of the pinion gear 250 engage with gear teeth formed on thesurface of the rack bar 260.

The rack bar 260 is a rodlike member for transmitting a steering force,which extends in a vehicle lateral direction. The gear teeth formed onthe surface of the rack bar 260 engage with the gear teeth on the piniongear 250 side described above. The rack bar 260 is configured to convertthe rotational motion of the pinion gear 250 to a linear motion in thevehicle lateral direction. On the other hand, on each of the both endsof the rack bar 260, there are coupled a tie rod and a knuckle (whosereference numerals are omitted) via which each steered wheel is coupled.Therefore, due to the linear motion in the vehicle lateral direction ofthe rack bar 260, each steered wheel can be steered in a horizontalsteering direction. In other words, in the steering mechanism 200, aso-called rack and pinion type steering mechanism is realized by thepinion gear 250 and the rack bar 260.

The EPS actuator 300 is an electric actuator provided with an EPS motor(not illustrated) as a DC brushless motor including: a not-illustratedrotor as a rotator to which a permanent magnet is attached; and a statoras a stationary part which surrounds the rotor. The EPS motor cangenerate an assist steering torque TA in the direction of rotation ofthe rotor, which is rotated by the action of a rotating magnetic fieldformed in the EPS motor due to the electrification to the stator via theEPS driving apparatus 400.

On the other hand, a not-illustrated reduction gear is fixed to a motorshaft as the rotating shaft of the EPS motor, and the reduction gearalso engages with the pinion gear 250. Thus, the assist steering torqueTA generated from the EPS motor functions as a torque for assisting therotation of the pinion gear 250. The pinion gear 250 is coupled with thelower steering shaft 240 as described above, and the lower steeringshaft 240 is coupled with the upper steering shaft 230 via the VGRSactuator 500. Therefore, a steering torque MT applied to the uppersteering shaft 230 via the steering wheel 210 is transmitted to the rackbar 260 in the form that it is assisted by the assist steering torqueTA, as occasion demands, by which the driver's steering load is reduced.

The EPS driving apparatus 400 is an electric drive circuit, including aPWM circuit, a transistor circuit, an inverter, and the like, capable ofelectrifying the stator of the EPS motor. The EPS driving apparatus 400is electrically connected to a not-illustrated battery, and it cansupply a driving voltage to the EPS motor by using an electric powersupplied from the battery. Moreover, the EPS driving apparatus 400 iselectrically connected to the ECU 100, and its operations are controlledby the ECU 100.

Incidentally, in the embodiment, the EPS actuator 300 and the EPSdriving apparatus 400 constitute a type of electronically-controlledpower steering apparatus. The structure of this type of power steeringapparatus for assisting the steering torque MT is not limited to what isexemplified here. For example, the assist steering torque TA outputtedfrom the EPS motor may be directly transmitted to the lower steeringshaft 240 with a reduction in a rotational speed by the not-illustratedreduction gear, or it may be applied as a force for assisting thereciprocating motion of the rack bar 260.

The VGRS actuator 500 is a rudder angle transmission ratio varyingdevice provided with a housing, a VGRS motor, and a reduction gearmechanism (each of which is not illustrated).

The housing is a case for accommodating the VGRS motor and the reductiongear mechanism. The end on the downstream side of the upper steeringshaft 230 is fixed to the housing. The housing and the upper steeringshaft 230 can rotate substantially integrally.

The VGRS motor is a DC brushless motor having a rotor as a rotator, astator as a stationary part, and a rotating shaft as the output shaft ofa driving force. The stator is fixed to the inside of the housing, andthe rotor is rotatably held within the housing. The rotating shaft iscoaxially rotatably fixed to the rotor, and its end on the downstreamside is coupled with the reduction gear mechanism.

The reduction gear mechanism is a planetary gear mechanism having aplurality of rotational elements which can perform differential rotation(a sun gear, a carrier, and a ring gear). Of the plurality of rotationalelements, the sun gear as the first rotational element is coupled withthe rotating shaft of the VGRS motor, and the carrier as the secondrotational element is coupled with the housing. Moreover, the ring gearas the third rotational element is coupled with the lower steering shaft240.

According to the reduction gear mechanism having such a structure, therotation angle of the upper steering shaft 230 according to a steeringangle MA as the operating angle of the steering wheel 210 (i.e. therotational angle of the housing coupled with the carrier) and therotation angle of the VGRS motor (i.e. the rotational angle of therotating shaft coupled with the sun gear) uniquely determine therotation angle of the lower steering shaft 240 coupled with the ringgear as the remaining one rotational element.

At this time, it is possible to perform increase/reduction control onthe rotational speed of the lower steering shaft 240 by performingincrease/reduction control on the rotational speed of the VGRS motor bymeans of the differential action between the rotational elements. Inother words, the upper steering shaft 230 and the lower steering shaft240 can perform relative rotation by the action of the VGRS motor andthe reduction gear mechanism. Moreover, in terms of the structure ofeach rotational element in the reduction gear mechanism, the rotationalspeed of the VGRS motor is transmitted to the lower steering shaft 240in the state that it is reduced in accordance with a predeterminedreduction ratio determined in accordance with a gear ratio between therotational elements.

As described above, in the vehicle 10, since the upper steering shaft230 and the lower steering shaft 240 can perform the relative rotation,a rudder angle transmission ratio is continuously variable in apredetermined set range, wherein the rudder angle transmission ratio isa ratio between the steering angle MA as the rotation angle of the uppersteering shaft 230 and an actual rudder angle δr of the steered wheelswhich is uniquely determined according to the rotation angle of thelower steering shaft 240 (which is also related to the gear ratio of arack and pinion mechanism described later). Incidentally, the rudderangle transmission ratio may be defined practically in any manner;however, it is defined as MA/δr here.

Incidentally, the reduction gear mechanism may have not only theplanetary gear mechanism exemplified here but also another aspect (e.g.an aspect in which gears, each having the different number of teeth, arecoupled with the upper steering shaft 230 and the lower steering shaft240, in which a flexible gear in contact with each of the gears in oneportion is set, and in which the flexible gear is rotated by using amotor torque transmitted via a wave generator, thereby relativelyrotating the upper steering shaft 230 and the lower steering shaft 240,or similar aspects). Alternatively, the reduction gear mechanism mayhave a physical, mechanical, or mechanistic aspect different from theaforementioned aspect even in the planetary gear mechanism.

The VGRS driving apparatus 600 is an electric drive circuit, including aPWM circuit, a transistor circuit, an inverter, and the like, capable ofelectrifying the stator of the VGRS motor. By driving the VGRS actuator200, the VGRS driving apparatus 600 functions as the rudder angletransmission ratio varying apparatus together with the VGRS actuator.The VGRS driving apparatus 600 is electrically connected to anot-illustrated battery, and it can supply a driving voltage to the VGRSmotor by using an electric power supplied from the battery. Moreover,the VGRS driving apparatus 600 is electrically connected to the ECU 100,and its operation is controlled by the ECU 100.

Here, the steering mechanism 200 in the embodiment, the EPS actuator300, and the VGRS actuator 500 constitute one example of the “steeringmechanism capable of changing the rudder angle of the steered wheelsregardless of the steering input of the driver” in the presentinvention. Explaining it more specifically, the EPS actuator 300 canapply to the steered wheels a steering force for promoting the steeringof the steered wheels. The rotation of the pinion gear 250 which causesthe linear motion of the rack bar 260 is accompanied by the rotation ofthe lower steering shaft 240 if nothing is done. Thus, under a constantrudder angle transmission ratio, a relation between the steering angleMA and a rudder angle δst does not change. In other words, it ispossible to promote the steering of the steered wheels independently ofthe driver's will; however, as a result, the steering wheel 210 willalso rotate independently of the driver's will.

Thus, the VGRS actuator 500 is driven in a form of synchronization withthe control of the EPS actuator 300 as described above. Explaining itmore specifically, when the steered wheels are changed independently ofthe driver's will by applying a driving force (the assist steeringtorque TA) from the EPS actuator 300, the VGRS actuator 500 reduces therudder angle transmission ratio. In other words, according to theprevious definition, the VGRS motor is controlled such that the steeringangle MA (or actual rudder angle δst) required to obtain one actualrudder angle δst is reduced (or increased). As a result, even if the EPSactuator 300 changes the actual rudder angle δst of the steered wheels,the rotation of the lower steering shaft 240 accompanied by that ishardly transmitted to the upper steering shaft 230, and it no longercauses the rotation of the steering wheel 210.

Further to that, the VGRS actuator 300 is in a form in which the VGRSmotor is so-called in the air. If it is tried to realize this type ofsteering by using only the VGRS actuator 500, instead of the steeredwheels being steered, the steering wheel 210 is steered in the oppositedirection. Therefore, there can be a difficulty in practice in coveringthe application of the steering force to the steered wheels only withthe VGRS actuator 500. In other words, by cooperatively controlling theEPS actuator 300 and the VGRS actuator 500, this type of steering can bepreferably realized.

On the other hand, the vehicle 10 is provided with a steering anglesensor 11, a steering torque sensor 12, a vehicle speed sensor 13, a yawrate sensor 14, a directional indicator light 15, a winker lever 16, andan in-vehicle camera 17.

The steering angle sensor 11 is a sensor capable of detecting thesteering angle MA which indicates the amount of rotation of the uppersteering shaft 230. The steering angle sensor 11 is electricallyconnected to the ECU 100, and the detected steering angle MA is referredto by the ECU 100 with a constant or irregular period.

The steering torque sensor 12 is a sensor capable of detecting thesteering torque MT given via the steering wheel 11 from the driver.Explaining it more specifically, the upper steering shaft 230 has such astructure that it is divided into an upstream part and a downstream partand that the parts are mutually coupled by using a not-illustratedtorsion bar. To the both ends on the upstream side and the downstreamside of the torsion bar, rings for detecting a rotational phasedifference are fixed. The torsion bar is twisted in its rotationaldirection in accordance with the steering torque transmitted via theupstream part of the upper steering shaft 230 when the driver of thevehicle 10 operates the steering wheel 210, and the steering torque canbe transmitted to the downstream part with the twist generated.Therefore, upon the transmission of the steering torque, there is therotational phase difference between the rings for detecting therotational phase difference described above. The steering torque sensor12 can detect the rotational phase difference, convert the rotationalphase difference to the steering torque, and output it as an electricalsignal corresponding to the steering torque MT. Moreover, the steeringtorque sensor 12 is electrically connected to the ECU 100, and thedetected steering torque MT is referred to by the ECU 100 with aconstant or irregular period.

The vehicle speed sensor 13 is a sensor capable of detecting a vehiclespeed V as the speed or velocity of the vehicle 10. The vehicle speedsensor 13 is electrically connected to the ECU 100, and the detectedvehicle speed V is referred to by the ECU 100 with a constant orirregular period.

The yaw rate sensor 14 is a sensor capable of detecting a yaw rate γ asthe speed or velocity in the yaw direction of the vehicle 10. The yawrate sensor 14 is electrically connected to the ECU 100, and thedetected yaw rate γ is referred to by the ECU 100 with a constant orirregular period.

The directional indicator light 15 is an indicator for indicating adirection for announcing the moving direction of the vehicle 10. Pair ofthe directional indicator lights 15 are disposed on either sides in thefront part, rear part, door mirror part, and meter hood in front of adriver's seat of the vehicle 10. The directional indicator light 15 iscoupled with a light driving part electrically connected to anot-illustrated battery, and it blinks at proper time intervals due tothe supply of an electric power from the light driving part.

The winker lever 16 is an operating device fixed on the left side of thesteering column 220 such that it can turn in the vertical direction.With regard to the winker lever 16, an upward direction with thesteering wheel 210 in the front corresponds to a right direction, and adownward direction corresponds to a left direction (incidentally,depending on the type of the vehicle, the winker lever 16 may bedisposed on the right side of the steering column 220, and the upwarddirection and the downward direction correspond to the left directionand the right direction, respectively). The directional indicator light15 and its operations are linked such that if the winker lever 16 isoperated to a lock position in one turning direction, the directionalindicator light 15 corresponding to the turning direction blinks.Moreover, if the winker lever 16 is returned to a neutral position fromthe lock position, accordingly, the blinking of the directionalindicator light 15 is also ended.

The winker lever 16 operated to the lock position is physically lockedat the lock position by a locking mechanism disposed in the steeringcolumn 220. The locking of the winker lever 16 is released if the winkerlever 16 is forcibly returned to the neutral position by the driver orif a winker-off process associated with winker-off control describedlater is performed.

Incidentally, the light driving part of the directional indicator light15 described above and the locking mechanism are electrically connectedto the ECU 100, and they are drive-controlled by the ECU 100. The winkerlever 16 (including the locking mechanism) and the directional indicatorlight 15 (including the light driving device) are one example of the“direction indicator” of the present invention, which constitutes aso-called winker apparatus. Hereinafter, in collectively calling them, aword of “direction indicator” will be used as occasion demands.

The in-vehicle camera 17 is an imaging apparatus which is disposed onthe front nose or front bumper of the vehicle 10 or the like and whichcan image a predetermined area ahead of the vehicle 10. The in-vehiclecamera 17 is electrically connected to the ECU 100, and the imaged areaahead is sent out to the ECU 100 as image data with a constant orirregular period. The ECU 100 can analyze the image data and obtainvarious data necessary for LKA control described later.

Operations in Embodiment Details of LKA Control

In the vehicle 10, as one of driving assist control of the vehicle 10,the LKA control is performed by the ECU 100. Incidentally, the LKAcontrol is control for making the vehicle 10 follow a target drivingroute (lane), and it is one example of the “lane keeping control” of thepresent invention. The LKA control is performed generally as follows.

The ECU 100 judges whether or not a LKA mode is selected (i.e. oneexample of the “lane keeping request” of the present invention) as aresult of such an operation that an operation button for initiating theLKA control disposed in the vehicle interior of the vehicle 10 inadvance is operated by the driver. If the LKA mode is selected, the ECU100 calculates various road surface information required when thevehicle 10 is made to follow the target driving route, on the basis of awhite line (incidentally, which is not necessarily white) for definingthe target driving route of the LKA, which is detected by using theimage data sent out from the in-vehicle camera 17. Incidentally, as theroad surface information, a curvature R of the target driving route(i.e. inverse of a radius), a lateral deviation Y between the white lineand the vehicle 10, and a yaw angle deviation φ between the white lineand the vehicle 10 or the like are calculated. Incidentally, an aspectof calculating information required for the control to follow the targetdriving route of this type can apply various aspects including a knownimage recognition algorithm, and it has a weak correlation with theessential part of the present invention. Thus, the calculation aspectwill not be mentioned herein.

If calculating the various road surface information, the ECU 100calculates target lateral acceleration necessary to make the vehicle 10follow the target driving route. Incidentally, at this time, the targetlateral acceleration can be also calculated in accordance with variousknown algorithms or arithmetic expressions. Alternatively, a targetlateral acceleration map or the like may be referred to, wherein thetarget lateral acceleration map uses the curvature R, the lateraldeviation Y and the yaw angle deviation φ described above as parametersand it is stored in a proper storing device such as a ROM. Ifcalculating the target lateral acceleration, the ECU 100 calculates aLKA target assist torque and controls the EPS actuator 300 on the basisof the calculated LKA target assist torque, thereby generating theassist steering torque TA corresponding to the LKA target assist torque.

Moreover, at this time, the VGRS actuator 500 is drive-controlled suchthat a change in the rudder angle δst for making the vehicle 10 followthe target driving route does not appear as a change in the behavior ofthe steering wheels 210 (i.e. a change in the steering angle MA). As aresult, the driver only needs to almost hold the steering wheel 210, andin the situation that the generation of an uncomfortable feeling issuppressed, the vehicle 10 can drive while following the target drivingroute. Incidentally, the LKA control as described above is merely oneexample of the control for making the vehicle 10 follow the targetdriving route, and its practical aspect can adopt various known aspects.

On the other hand, this type of driving assist function is not performedbeyond the driver's will. Thus, the ECU 100 stops this type of drivingassist without delay if the steering will is shown by the driver. Withregard to the LKA control, the ECU 100 ends the LKA control if theoperation of the steering wheel 210, the operation of the brake pedal,or the operation of the winker lever 16 is performed. Incidentally, inending the LKA control, the assist steering torque TA supplied by theEPS actuator 300 at that time point is gradually reduced in accordancewith the vehicle speed V. In other words, the gradual reduction periodis longer on the higher speed side. As described above, the gradualreduction process according to the vehicle speed V is performed, bywhich it is prevented that the vehicle behavior is destabilized beforeand after the end of the LKA control.

Details of LKA End Control

The LKA control as described above needs to be ended if the driver showsa clear steering will. If the operation of the winker lever 16 isperformed as an action for indicating such a steering will, since asteering input is not accompanied, the vehicle 10 deflects in adirection different from the direction intended by the driver in somecases. Thus, the ECU 100 can end the LKA control accurately if thewinker lever 16 is operated, by performing the LKA end control.

Now, with reference to FIG. 2, the details of the LKA end control willbe explained. FIG. 2 is a flowchart showing the LKA end control.

In FIG. 2, the ECU 100 judges whether or not the LKA control isperformed (step S101). If the LKA control is not performed (the stepS101: NO), the process operation in the step S101 is repeatedlyperformed. If the LKA control is performed (the step S101: YES), the ECU100 judges whether or not there is a direction indicating operation viathe winker lever 16 (step S102). If there is no direction indicatingoperation (the step S102: NO), the process is returned to the step S101.

On the other hand, if there is the direction indicating operation (thestep S102: YES), the ECU 100 performs a LKA end judging process (stepS200). If the LKA end judging process is performed, the process isreturned to the step S101, and a series of process operations isrepeated. The LKA end control is performed in this manner.

Next with reference to FIG. 3, the details of the LKA end control willbe explained. FIG. 3 is a flowchart showing the LKA end contorl.

In FIG. 3, the ECU 100 judges whether or not the indicated direction ofthe winker lever 16 is equal to a generation direction of generating theassist steering torque TA (i.e. the steering torque corresponding to theLKA target assist torque described above) (step S201). If the indicateddirection is different from the generation direction of the assiststeering torque TA (the step S201: NO), the ECU 100 moves the process toa step S204.

On the other hand, if the indicated direction is equal to the directionof the assist steering torque TA (the step S201: YES), the ECU 100judges whether or not a steering angle MAdrv corresponding to thedriver's steering input is less than or equal to a steering angle MAlkagenerated by the LKA control (step S202). If the steering angle MAdrv isgreater than the steering angle MAlka (the step S202: NO), i.e. if thereis the driver's steering input exceeding the amount of controlassociated with the LKA control, the ECU 100 moves the process to thestep S204.

If the steering angle MAdrv is less than or equal to the steering angleMAlka (the step S202: YES), the ECU 100 judges whether or not thevehicle 10 departs from the target driving route associated with the LKAcontrol (step S203). If the vehicle 10 does not depart from the targetdriving route (the step S203: NO), the ECU 100 returns the process tothe step S202. Moreover, if the vehicle 10 departs from the targetdriving route (the step S203: YES), the ECU 100 moves the process to thestep S204.

In the step S204, the LKA control is ended. If the LKA control is ended,the LKA end judging process is ended, and the process is returned to theLKA end control.

As described above, according to the embodiment, when the LKA control isended by the direction indicating operation performed by the winkerlever 16, if the indicated direction of the winker lever 16 is differentfrom the generation direction of the assist steering torque TA, thedirection of the deflection which occurs in the vehicle 10 with thegradual reduction in the assist steering torque TA in ending the LKAcontrol is a direction equal to the driver's steering will. Thus, underthe judgment that the uncomfortable feeling is not generated, the LKAcontrol is promptly ended. On the other hand, if the indicated directionis equal to the generation direction of the assist steering torque TA,the direction of the deflection which occurs in the vehicle 10 with thegradual reduction in the assist steering torque TA in ending the LKAcontrol is likely a direction opposite to the driver's steering will.Thus, the end of the LKA control is suspended until the steering angleMAdrv corresponding to the driver's steering input exceeds the steeringangle MAlka generated by the LKA control. On the other hand, even in aperiod in which the end of the LKA control is suspended because thesteering angle MAdrv is less than or equal to the steering angle MAlka,if the vehicle 10 departs from the target driving route, the LKA controlis ended under the assumption that the driver's steering will is alreadysufficiently reflected and that the generation of the uncomfortablefeeling can be ignored. Thus, if the operation of the winker lever 16 isperformed, it is possible to end the LKA control accurately.

SECOND EMBODIMENT

In the LKA end control illustrated in FIG. 2, the LKA end judgingprocess in the step S202 can be replaced by another process. Here, asecond embodiment of the present invention based on the purpose will beexplained with reference to FIG. 4. FIG. 4 is a flowchart showing theLKA end judging process in the second embodiment of the presentinvention. Incidentally, in FIG. 4, portions overlapping those of FIG. 3will carry the same reference numerals, and the explanation thereof willbe omitted as occasion demands.

In FIG. 4, the ECU 100 judges whether or not the steering torque MT asthe driver's steering input exceeds a steering torque threshold valueMTth (step S301). If the steering torque MT is less than or equal to thesteering torque threshold value MTth (the step S301: NO), the processoperation in the step S301 is repeatedly performed. On the other hand,if the steering torque MT exceeds the steering torque threshold valueMTth (the step S301: YES), the ECU 100 ends the LKA control (the stepS204).

Now, with reference to FIG. 5, an explanation will be given on thedetails of the steering torque threshold value MTth used for thecomparative judgment with the steering torque MT. FIG. 5 is a schematiccharacteristic diagram showing a relation between the steering torque MTand the steering torque threshold value MTth.

As shown in FIG. 5, the steering torque threshold value MTth is afunction of the steering torque MT, and it is set to be large in an areain which the steering torque MT is small, and it is set to be small inan area in which the steering torque MT is large (incidentally, there isalso a gradual reduction area as shown). Here, the steering torque MTinputted by the driver is overridden by the assist torque TA supplied bythe EPS actuator 300. Thus, if the steering direction intended by thedriver (i.e. a generation direction of generating the steering torqueMT) is equal to the generation direction of the assist torque TA, thesteering torque MT is relatively small. On the other hand, if thesteering direction intended by the driver (i.e. the direction ofgenerating the steering torque MT) is opposite to the generationdirection of the assist torque TA, the steering torque MT needs to berelatively large.

In other words, in the area in which the steering torque MT isrelatively small, the vehicle 10 deflects in a direction different fromthe generation direction of the steering torque MT due to the gradualdecrease in the assist torque TA caused by the end of the LKA control.In the area in which the steering torque MT is relatively large, thevehicle 10 deflects in the generation direction of the steering torqueMT due to the gradual decrease in the assist torque TA caused by the endof the LKA control.

In view of this point, in the area in which the steering torque MT isrelatively small, the steering torque threshold value MTth is set to belarge, and the end of the LKA control is delayed (incidentally, there isno problem because the vehicle 10 is steering-controlled in a desireddirection due to the assist steering torque TA) until the relativelylarge steering torque MT (namely corresponding to the driver's clearsteering will) is generated. In the area in which the steering torque MTis relatively large, the steering torque threshold value MTth is set tobe small, and the LKA control is promptly ended (incidentally, there isno problem because the vehicle 10 is steering-controlled in a desireddirection due to the gradual reduction in the assist steering torqueTA). Thus, it is possible to accurately end the LKA control, which doesnot cause the driver to have the uncomfortable feeling.

The present invention is not limited to the aforementioned embodiments,but various changes may be made, if desired, without departing from theessence or spirit of the invention which can be read from the claims andthe entire specification. A control apparatus for a vehicle, whichinvolves such changes, is also intended to be within the technical scopeof the present invention.

DESCRIPTION OF REFERENCE CODES

FL, FR steered wheels

10 vehicle

11 steering angle sensor

12 steering torque sensor

13 vehicle speed sensor

14 yaw rate sensor

15 directional indicator light

16 winker lever

17 in-vehicle camera

100 ECU

200 steering mechanism

210 steering wheel

220 steering column

230 upper steering shaft

240 lower steering shaft

250 pinion gear

260 rack bar

300 EPS actuator

400 EPS driving apparatus

500 VGRS actuator

600 VGRS driving apparatus

INDUSTRIAL APPLICABILITY

The present invention can be applied to a vehicle capable of performinglane keeping control by using a steering mechanism for changing a rudderangle regardless of a driver's steering input.

1. A control apparatus for a vehicle comprising a steering mechanism capable of changing a rudder angle of steered wheels regardless of a driver's steering input, said control apparatus comprising: a performing device for performing predetermined lane keeping control for controlling the steering mechanism such that the vehicle does not depart from a target driving route, in response to a lane keeping request; and an ending device for ending the lane keeping control on the basis of an operating state of a direction indicator and a control state of the steering mechanism in a period of performing the lane keeping control.
 2. The control apparatus for the vehicle according to claim 1, wherein the control state is a generation direction of generating a steering torque in a course of performing the lane keeping control, the operating state is an indicated direction of the direction indicator, and said ending device changes end timing of the lane keeping control in accordance with whether or not the generation direction is equal to the indicated direction.
 3. The control apparatus for the vehicle according to claim 2, wherein said ending device ends the lane keeping control belatedly in comparison with a case where the generation direction is different from the indicated direction, if the generation direction is equal to the indicated direction.
 4. The control apparatus for the vehicle according to claim 2, wherein said ending device ends the lane keeping control after the steering input is performed, if the generation direction is equal to the indicated direction.
 5. The control apparatus for the vehicle according to claim 2, wherein said ending device ends the lane keeping control at a time point of performing an operation of the direction indicator, if the generation direction is different from the indicated direction.
 6. The control apparatus for the vehicle according to claim 1, wherein said ending device ends the lane keeping control if a steering torque is inputted and the inputted steering torque exceeds a threshold value determined in accordance with the inputted steering torque in a case where the direction indicator is operated. 